1. Field Of The Invention
The present invention relates to improvements in the cement-concrete structures in general and to the following in particular: 1) general purpose and pre-stressed concrete (typically up to 6000 p.s.i. (41.38 MPa)); 2) exterior-interior cement board; 3) mortar; 4) concrete masonry units; and 5) concrete pipe.
2. General Background
Conventional concrete is a mixture of portland cement (including 3CaO.cndot.SiO.sub.2, 2CaO.cndot.SiO.sub.2, 3CaO.cndot.Al.sub.2 O.sub.3, 4CaO.cndot.Al.sub.2 O.sub.3 .cndot.Fe.sub.2 O.sub.3), sand, aggregate and water. Fly ash is now being used in combination with portland cement in many portland-cement-based products.
Information about portland cement and conventional concrete can be found in Design and Control of Concrete Mixtures, 13th ed. 1988, a booklet produced by the Portland Cement Association, Skokie, Ill.; unless specified otherwise, when the term "concrete" is used herein, it refers to concrete as described in this booklet "Cement", as used herein and unless specified otherwise, refers to the building material described in ASTM (American Society for Testing and Materials) standards and used to make, for example, the building material commonly referred to as concrete. Information about concrete masonry units can be found in Section 4, volume 04.05, pages 68-70 of the 1989 Annual Book of ASTM Standards, and in a brochure of Sherman Industries South Alabama Division, Mobile, Ala., entitled "Precast and Concrete Masonry Units". General information about masonry construction can be found in Structural Details for Masonry Construction by Morton Newman and published in New York by McGraw-Hill in 1988 and in Concrete Masonry Handbook for Architects, Engineers, Builder by Frank A. Randall, Jr. and William C. Panarese (Portland Cement Association 1976).
It has been found that cements containing 1% or more of sodium oxide and potassium oxide will react with aggregates containing opaline silica, highly siliceous rocks and limestone. The formation of the new compounds causes the interior of the concrete to expand, resulting in surface cracking, which for years has been accepted as natural to its use.
Reinforced (steel) concrete was invented by Thaddeus Hatt in 1878, U.S. Pat. No. 206,112 and over the years many improvements have been made in the use of inorganic fibers and others, such as alumina, asbestos, glass, graphite, etc.; the features of which are disclosed, for example, in U.S. Pat. Nos. 3,992,172; 4,316,925; and 4,337,094. Information about fiber-reinforced concrete can be found in State-of-the-Art Report on Fiber Reinforced Concrete, publication number ACI 544.1R-82 (reapproved 1986) of the American Concrete Institute, Detroit, Mich.; this publication discloses the use of fibers made of such plastics as nylon, polypropylene, polyethylene, polyester, and rayon.
Cement board is described in Durock Exterior Cement Board Systems (publication number SA-700/1-92--1992 ed. of the United States Gypsum Company). Methods of making cement board are described in U.S. Pat. Nos. 4,916,004; 4,504,335; 4,488,909; and 4,450,022. U.S. Pat. No. 4,504,335 discloses the use of aramid fibers in cement board.
Tilt-up concrete walls are described in an article entitled "New technique used to raise walls" by Ron Colquitt on page 1 of Section D of the Aug. 11, 1991 edition of the Mobile Press Register.
Concrete is sometimes used to whitetop deteriorating asphalt pavements. See Whitetopping an Asphalt Parking Area, publication number PA152.01B of the Portland Cement Association, Skokie, Ill.
Used automobile and truck tires and other scrap rubber are a national environmental problem. Various proposals have been made to deal with the problem, and many of these proposals are being tested. See, for example, Scrap Tire Use/Disposal Study--1992 Update, an October 1992 publication by A. T. Kearney and available from the Scrap Tire Management Council, Washington, D.C., which describes, among other proposals, the use of scrap tire material in asphalt/paving applications. However, the study does not report favorably on the use of scrap tire material in asphalt/paving applications. An article by Tom Arrandale entitled "Scrap tires a nightmare for solid waste managers" appearing on page 7-B of the May 22, 1992 edition of The Mobile Press describes the problems caused by the disposal of old tires.
Cowper, U.K. Pat. No. 338,247, describes a road material which comprises primarily rubber, including crumbed rubber, and includes a small amount of cement. According to the patent, the material can be formed into blocks, bricks, slabs, or sheets.
McDonald, U.S. Pat. No. 3,891,585, discloses an asphalt/rubber pavement material. The preferred size of the rubber particles used therein is stated to be 4 to +200 mesh U.S. Sieve Series. U.S. Pat. No. 3,930,100 discloses a similar material.
Portin, U.S. Pat. No. 4,082,888 discloses a rubber-based paving composition. It does not include cement.
Thelen et al., U.S. Pat. No. 4,564,310, discloses a paving material whose major component by weight consists of scrap rubber from tires. It does not include cement.
Firestone, U.K. Pat. No. 763,395, describes a rubber-containing asphalt paving composition. It does not include cement.
Soviet Patent No. 607,868 discloses a road material including asphalt and rubber crumb, but apparently not including cement.
Japanese Patent publication number 57-92203 discloses a road material which contains asphalt, rubber, and may comprise cement as a filler.
Haynes et al., U.S. Pat. No. 4,330,632, discloses a lightweight concrete which includes polymer-filled aggregate particles. The concrete described in this patent would cost approximately ten times the cost of conventional concrete. In this invention, the polymer serves as a binder.
Chung, U.S. Pat. No. 5,032,181, discloses carbon-fiber-reinforced cement-concrete, with the carbon fibers being present in an amount of about 0.1% to about 4% by weight of the cement. However, as pointed out in Chung, carbon fibers are costly.
Automobiles are up to 16% more efficient when travelling on concrete as compared to asphalt. However, concrete is sometimes passed over for use on roads because of its tendency to crack with time.
An article entitled "Holnam gives up on waste" on page B1 of the Dec. 12, 1992 issue of the Mobile Register newspaper discloses a proposal to use scrap tires to make cement. The scrap tires would be used as a kiln fuel to heat raw materials. Residue from the fuel would be mixed into other raw materials. However, there would be little, if any, rubber left in the residue.
The Summer 1992 issue of Scrap Tire Connection, the Newsletter of the Scrap Tire Management Council, is devoted to the use of scrap rubber from tires in asphalt pavement. The Newsletter describes the benefits of using rubber in asphalt, but it does not suggest that rubber can be used in concrete.
All publications mentioned herein are hereby incorporated by reference.
All measurements mentioned herein are at standard temperature and pressure, unless otherwise stated.